Ebullated bed coal hydrogenation



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Nv D 505mm 5025 United States Patent O 3,519,555 EBULLATED BED COAL HYDRGENATION Percival C. Keith, Peapack, Edwin S. Johanson, Princeton, Ronald H. Wolk, Lawrence Township, Mercer County, and Seymour B. Alpert and Seymour C. Schuman, Princeton, NJ., assiguors to Hydrocarbon Research, Inc., New York, N.Y., a corporation of New Jersey Continuation of application Ser. No. 602,713, Dec. 19, 1966, and a continuation-impart of application Ser. No. 340,899, Jan. 29, 1964. This application Nov. 8, 1968, Ser. No. 774,540

Int. Cl. Cg 1/08 U.S. Cl. 208-10 9 Claims ABSTRACT OF THE DISCLOSURE A coal hydrogenation process employing an expanded catalyst bed and producing better than 80% conversion of coal to gas and liquid petroleum products.

CROSS REFERENCES TO RELATED APPLICATION This application is a continuation of application, Ser. No. 602,713, tiled Dec. 19, 1966, now abandoned, and a continuation-impart of the application, Coal Hydrogenation, Ser. No. 340,899, iiled Jan. 29, 1964, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the hydrogenation of coal for the production of liquid and gaseous fuels.

It is recognized that in several regions of the Uhited States there are abundant supplies of various types of coal including bituminous, semi-bituminous and subbituminous grades, as well as lignites which are available at very low unit fuel value and which have high potential value if they could be economically converted to more desirable fuel forms such as liquids and gaseous hydrocarbons of high hydrogen content. This raw material would be of great importance notwithstanding the fact that liquid hydrocarbons are plentiful in many parts of the world since a competitive process would take advantage of the large quantities of afvailable coals and the industrial capability of the adjacent area to supply the liquid and gaseous hydrocarbon requirements of that area.

The conversion and utilization of coal to produce other, more valuable fuel products has been actively carried out for more than a century. With the advent of the internal combustion engine and with relatively limited petroleum supplies in some countries of the world, technical efforts were accelerated to convert coal to liquid fuels. In many cases, this work 'was supported by the military lwho realized the need for a dependable supply of liquid fuels in case of war, utilizing available coal deposits.

In certain countries foreign to the United States, oil made from coal has reached a maximum output of over tive million metric tons per year (or about one hundred thousand barrels per day). This oil was used as aviation fuel, motor gasoline, diesel oil and heavy fuel oil. To a very large extent, this was accomplished by a high pressure hydrogenation which was usually carried out in the 5,000 to 10,000 p.s.i.g. pressure range. It was, of course, found that such processes were completely uneconomical compared with the use of natural petroleum and after the war-time urgency was over, all of the synthetic fuel plants in petroleum competitive areas such as in the United States, were shut down.

In the ten year period 1945-1955 following the war, extensive studies were carried out in the United States 3,519,555 Patented July 7, 1970 to increase the utilization of coal, due to the very large known reserves, uncertainty in liquid hydrocarbon supplies, and to avoid, or mitigate the economic depression in coal bearing areas. However, the increased availability of low cost liquid hydrocarbon fuels rendered uneconomical the production of high grade petroleum products from coal by the ultra-high pressure technology then available.

Under government as well as private sponsorship, the utilization of coal for conversion to liquid fuels has thus been under active study but with the presently established low economic promise for such processes, this work has been on a very reduced scale. While the fundamental knowledge of coal constitution and reactivity has been diligently studied, this economic appraisal has tended to restrict the work to the production of the more expensive but less used chemicals.

There are, of course, many mechanical problems in handling coal as well as the problems of high pressure hydrogenation. It is recognized that coal as a solid, flows with difficulty. It has a low hydrogen content and it contains ash. While these obstacles can be overcome technically, the development of a practical economic process for conversion of coal to more desirable free forms has not been possible because of the extreme conditions hitherto required in hydrogenation of raw coal.

SUMMARY Our invention provides a process for the hydrogenation of coal to more valuable products (both liquid and gas) utilizing low reactor pressures and achieving better than conversion of the coal. These products appear to be competitive or superior in cost and quality to available fuels and as a result of our invention, we can develop a nearly inexhaustible fuel source and industrially make afvailable, commercial competitive fuels. It is also possibe with our invention to provide either a high or low B.t.u. fuel gas such as methane and hydrogen-carbon monoxide mixture respectively or a natural gas substitute of about 1000 B.t.u., which can be placed in pipelines compatible in burning, flow, and metering characteristics with the usual natural gas.

To more effectively utilize coal, our invention takes advantage of a relatively newly developed technique generally known as ebullation which is more particularly described in the Johanson patent, 2,987,465. In such patent, it is noted that if a reaction zone is partially filled with particulate solids and a gas, such as hydrogen, is passed upwardly through the bed together with a liquid such as a hydrocarbon liquid, it is possible to obtain a greatly improved reaction due to the random motion of the particles, the limited pressure drop, and particularly due to the uniformity of temperature. It was found possible to hydrogenate coal, as described in such patent, as well as to carry out other chemical reactions.

Our present invention primarily accomplishes a relatively lower pressure hydrogenation of the solid coal particles in a slurry and in the presence of catalyst to convert better than 80% of the coal to a crude product oil. With suitable separating equipment such as absorbers and fractionators, it is thus possible to produce from coal desired quantities of liquid hydrocarbons such as No. 6 fuel oil, naphtha and gas of a controlled B.t.u. and gravity content.

DESCRIPTION OF DRAWING Further objects and advantages of ou1 invention will appear from the following description of a preferred form of embodiment thereof as more particularly shown in the attached drawing illustrative thereof, which drawing is a diagrammatic view of essential process equipment for the conversion of coal to valuable liquid and gaseous end products.

9 DESCRIPTION OF PREFERRED EMBODIMENTS As shown, a coal such as bituminous, semi-bituminous, sub-bituminous or lignite, or a similar material such as shale, entering the system at 10 is first passed through a preparation unit generally indicated at 12. In such a unit it is desirable to dry the coal of all surface moisture and to grind the coal to a desired mesh and then to screen it for uniformity. For our purposes, it is preferable that the coal has a lineness of about 100 mesh and is preferably of relatively close sizing, i.e., all passing 50 mesh and not less than 80% retained on 200 mesh. However, it will be observed that the preciseness of size may vary between different types of coal, lignite and shale.

The coal fines discharge at 14 into the transfer line 16 where the coal is blended with a carrying oil indicated at 18 which, as hereinafter pointed out, is conveniently made in the system. To establish an effective transportable slurry, it is found that the ground coal should be mixed with at least about an equal weight of carrying oil. In addition, a hydrogenation catalyst, if desired, may be added to 20 in the ratio of about 0.01 to 0.20 pound of catalyst per ton of coal. Such a catalyst would be from the class of cobalt, molybdenum, nickel, tin, iron and the like deposited on a base of the class of alumina, magnesia, silica, and the like. It is to be noted that the catalyst need not be added continuously nor is it required that it be in ne admixture with the coal.

The coal-oil slurry is then passed through the heater 22 to bring the slurry up to a temperature in the order of 750 F. to 950 F., or 800 F. to 900 F., such heated slurry then discharging at 24 into the reactor feed line 26 wherein it is supplied with make-up hydrogen from the line 28 as well as recycle hydrogen in line 46.

The entire mixture of hydrogen and coal-oil slurry then enters one or more reactors 30 passing upwardly from the bottom at a rate and under pressure and at a temperature to accomplish the desired hydrogenation.

By concurrently owing streams of liquid and gasiform materials upwardly through a vessel containing a mass of solid particles of a contact material which may be a specific catalyst as above indicated, and expanding the mass of solid particles at least 10% over the volume of the stationary mass, the solid particles are placed in random motion within the vessel by the upfiowing streams. A mass of solid particles in this state of random motion in a liquid medium may be described as ebullated The characteristics of the ebullated mass at a prescribed degree of volume expansion can be such that a finer, lighter solid will pass upwardly through the mass so that the particles constituting the ebullated mass are retained in the reactor and the finer, lighter material may pass from the reactor.

The contact material (herein catalyst) is preferably in the form of beads, pellets, lumps, chips or like particles at least 1/32 inch and more frequently in the range of 1/16 to 1A, inch (i.e., between about 3 and 14 mesh screens of the Tyler scale). The size and shape of the particles used in any specific process will depend on the particular conditions of that process, eg., the density, viscosity and velocity of the liquid involved in that process and they may be separately introduced to the reactor 30 at 31.

It is a relatively simple matter to determine for any ebullated process the range of throughput rates of upflowing liquid which will cause the mass of solid particles to become expanded and at the same time placed in random motion. The gross volume of the mass of contact particles expands when ebullated without, however, any substantial quantity of the particles being carried away by the upflowing liquid and, therefore, a fairly Welldelined upper level of randomly moving particles establishes itself in the upflowing liquid. The upper level 32 above which few, if any, particles ascend will hereinafter be called the upper level of ebullation.

In contrast to processes in which fiuid streams flow downwardly or upwardly through a fixed mass of particles, the spaces between the particles of an ebullated mass are thus large with the result that the pressure drop of the liquid flowing through the ebullated mass is small and remains substantially constant so the fluid throughput rate is increased. Thus, a considerably smaller consumption of power is required for a given throughput rate. Moreover, the ebullated mass of particles promotes much better contact between the coal fines and gasiform streams than with any fixed bed process. Under these conditions, a significantly greater fluid throughput rate carrying the coal fines may be used without impairing the desired degree of contact than if conventional downflow or uptlow through a fixed bed of contact particles is used.

Moreover, solid material will pass through an ebullated bed where it would otherwise plug a fixed bed. Additionally, the random motion of particles in an ebullated mass causes these contact particles to rub against each other and against the walls of the vessel so that the formation of deposits thereon is impeded or minimized. The scouring action helps to prevent agglomeration of the contact particles and plugging up of the vessel. This effect is particularly important Where catalyst particles are employed and maximum contact between coal fines, hydrogen and the catalytic surfaces is desired, since the contact surfaces are exposed to the reactants for a greater period of time before becoming fouled or inactivated by foreign deposits.

The process of this invention may be carried out under a wide variety of conditions. To obtain the advantages of this invention it is only necessary that the liquid, coal fines, and gasiform materials flow upwardly through a mass of solid particles of a contact material at a rate causing the mass to reach an ebullated state. In each ebullated system, variables which may be adjusted to attain the desired ebullation include the iow rate, density and viscosity of the liquid and the gasiform material, and the size, shape and density of the particulate material. However, it is a relatively simple matter to operate any particular process so as to cause the mass of contact material employed to become ebullated and to calculate the percent expansion of the ebullated mass after observing its upper level of ebullation through a glass Window in the vessel, or by radiation or acoustic permeability, or by other means such as liquid samples drawn from the vessel at various levels. In general, the gross density of the stationary mass of contact material will be between about 25 and 200 pounds per cubic foot, the flow rate of the liquid will be between about 5 and 120 gallons per minute per square foot of horizontal cross section of the ebullated mass, and the expanded volume of the ebullated mass usually not more than about double the volume of the settled mass and preferably only about eight percent. A recycle liquid stream 34, which may be internal or external of the reactor, may be removed above the upper level of ebullation 32, heat tempered at 35 and recycled by pump 36 to the bottom of the reactor to maintain the desired superficial liquid velocity in the reactor 30. Spent catalyst may be removed from time to time by drawoff 37.

Preferred reactor operating conditions are in the range of 750 to 950 F. and less than 3000 p.s.i.g. Coal throughput is at the rate of 15-150 pounds per hour per cubic foot of reactor space so that the yeld of unreacted coal as char is between 5 and 25 percent of the quantity of moisture and ash free coal feed. The relative size of the coal and catalyst particles and condition of ebullation are such that the catalyst is retained in the reactor while the unreacted char is carried out with the reaction products and the slurry oil solid.

The degree of hydrogenation in reactor 30 can be limited to that which will leave sufficient unreacted coal to make hydrogen in a subsequent gasification stage. This hydrogen could then be recycled for use in the hydrogenation step. This type of process would be advantageous in areas where hydrogen is difficult to obtain.

However, with gasification, the -amount of conversion would be significantly reduced. The efliuent stream 38 passing to separator 40 includes a stream that contains gaseous fractions, is virtually free of solid particles of contact material although it may contain char in the liquid. From the separator 40 a gas stream is removed at 42 and then passed to absorber 44. A hydrogen recycle in line 46 removed from absorber 44 may be returned to the reactor 30 to supplement the hydrogen requirements. A liquid stream from the absorber 44 will be removed at 48 and this is joined with the liquid stream 49 from the high pressure separator 40. The joint liquid is then passed to a low pressure recovery system 50.

The low pressure separator 50 permits removal of a high B.t.u. gaseous product at 52 and a solids free liquid at 54. A separate liquid stream containing char is removed at 56. A portion of the liquid from line 54 may be used to prepare the initial slurry.

The invention will now be illustrated demonstrating the lmanner in which practical degrees of coal conversion can be achieved by this method and the process application of such degree of coal conversion for the complete utilization of coal without the use of auxiliary sources of hydrocarbons for the production of liquid and gaseous hydrocarbons of value.

EXAMPLE 1 Coal having 42% by weight of volatile matter and 10.6% by weight of ash on a moisture free basis was pulverized to pass through a 100 mesh screen and then admixed with hydrocarbon oil in the weight ratio of 3.3 parts of oil per part of coal. The coal-oil suspension was passed upwardly through a reactor 30 together with hydrogen. The reactor contained a mass of cobalt molybdate on alumina hydrogenation catalyst particles of uniform cylindrical size about 0.025 inch in diameter and 1A; inch in length. The coal-oil suspension flowed upward through the reactor at the rate of 20 gallons per minute per square foot of horizontal cross-section of the reactor thereby effecting ebullation of the catalyst particles with approximately 50% expansion of the settled volume of the catalyst mass to fill about 80% of the reactor space when in the expanded state. Hydrogen rich gas was supplied to the bottom of the reactor at the rate of 80,000 standard cubic feet for each ton of coal entering the reactor. The hydrogenation was conducted at a temperature of 830 F. and a pressure of 2,750 pounds per square inch gauge. The reaction effluent comprising coaloil suspension discharged from the reactor into a separator whence gasiform and liquid streams were separately withdrawn. Part of the eiuent liquid stream consisting of an oil suspension of partially hydrogenated coal particles Was recycled directly to the reactor at a rate of about 12 volumes per volume of slurry feed to maintain the aforesaid flow rate of 20 gallons per minute per square foot. The conversion of moisture and ash-free coal to liquid and gaseous products amounted to 82% of the weight of moisture and ash free coal feed.

EXAMPLE 2 The coal used was Illinois No. 6, Belleville area coal of the following analysis:

As received Dry lroximate analysis:

Percent moisture 11. 04 Percent ash 9. 38 10.54 Percent volatile 37. 99 42. 70 Percent fixed carbon 41. 59 46. 76

Ultimate analysis;

Percent moisture 11. 04 Percent carbon 62. 69. 81 Percent hydrogen 4. 53 5.09 Percent nitrogen. 1. 02 1.15 Percent chlorine.- 0.02 0.02 Percent sulfur 3.17 3. 56 Percent ash 9. 38 10. 54 Percent oxygen 8. 74 9. 80

6 The coal ground to pass 100 mesh screen was mixed with No. 4 fuel oil (24.9 API, 442-670" B.P.) at ratios of 0.1 to 0.3 lb. coal/ lb. oil for injection into the reaction system.

It is possible to obtain better than 90% yield at pressures significantly below 3000 p.s.i.g.

While we have shown and described a preferred form of embodiment of our invention, we are aware that modificatons may be made thereto and we, therefore, desire a broad interpretation of our invention within the scope and spirit of the description herein and of the claims appended hereinafter.

We claim:

1. The process of conversion of coal to petroleum-like hydrocarbons and fuel gas by a catalytic hydrogenation which comprises:

(a) drying, grinding and screening the coal to form a coal feed substantially moisture free, of relatively close sizing all passing 50 mesh;

(b) slurrying said coal feed with at least about an equal weight of a subsequently recovered liquid from the process having a boiling range substantially that of No. 4 fuel oil;

(c) adding a hydrogenation catalyst selected from the group consisting of cobalt, molybdenum, nickel, iron and tin supported on a base selected from the group consisting of alumina, magnesia and silica, such addition being at a minimum rate of about 0.01 pound per ton of coal, the catalyst being in the size range between about 3 and 14 mesh on the Tyler scale;

(d) passing said coal-oil-catalyst slurry upward through a reaction zone together with hydrogen with a coal feed rate between 15 and 150 pounds per hour per cubic foot of reaction zone, the liquid velocity being in the order of 10 to 120 gallons per minute per square foot of horizontal cross-section of the reaction zone;

(e) maintaining the reaction zone under a pressure of less than 3000 p.s.i.g. and a temperature in the range of 750 F. to 950 F.;

(f) removing a portion of the eiuent from the upper level of the reactor and recycling this effluent into the bottom of the reactor;

(g) withdrawing a reaction eiiiuent from the upper part of the reaction zone and separating from said effluent normally gaseous materials and a liquid containing char and ash and unreacted coal;

(h) the conversion of the carbon in the coal, on a moisture and ash free basis, being in excess of and the net oil production being greater than 70%.

2. In a process as claimed in claim 1 wherein the coal is Illinois No. 6, the hydrogen throughput is in the order of 43 standard cubic feet per pound of coal, the conversion of moisture ash free coal is greater than 3. In a process as claimed in claim 1 wherein a solids free liquid is recovered from the reaction efuent and is used as the subsequently recovered liquid in step (b).

4. In a process as claimed in claim 1 wherein the coal feed is slurried with a subsequently recovered liquid at ratios of 0.1 to 0.3 lb. coal/lbs. oil.

5. In a process as claimed in claim 1 wherein the normally gaseous materials are separated from the liquid containing char and ash and unreacted coal by means of a high pressure separator system.

6. In a process as claimed in claim 1 wherein the solids content of the subsequently recovered liquid is controlled by means of removal of solids by a low pressure separator system.

7. The process of conversion of coal to petroleum-like hydrocarbons and fuel gas by a catalytic hydrogenation which comprises:

(a) drying, grinding and screening the coal to form a coal feed susbtantially moisture free, of relatively close sizing all passing 50 mesh;

(b) slurrying said coal feed with a subsequently recovered liquid from the process having a boiling range substantially that of No. 4 fuel oil at ratios of 0.1 to 0.3 lb. coal/lbs oil;

(c) adding a hydrogenation catalyst selected from the group consisting of cobalt, molybdenum, nickel, iron and tin supported on a base selected from the group consisting of alumina, magnesia and silica, such addition being at a minimum rate of about 0.01 pound per ton of coal, the catalyst being in the size range between about 3 and 14 mesh on the Tyler scale;

(d) passing said coal-oil-catalyst slurry upward through a reaction zone together with hydrogen with a coal feed rate between and 150 pounds per hour per cubic foot of reaction zone, the liquid velocity being in the order of 10 to 120 gallons per minute per square foot of horizontal cross-section of the reaction zone;

(e) maintaining the reaction zone under a pressure of less than 3000 p.s.i.g. and a temperature in the range of 800 to 900 F.;

(f) removing a portion of the elliuent from the upper level of the reactor and recycling this euent into the bottom of the reactor;

(g) withdrawing a reaction eluent from the upper part of the reaction zone and separating from said efuent normally gaseous materials and a liquid containing char and ash and unreacted coal; (h) the conversion of the carbon in the coal, on a moisture and ash free basis, being in excess of and the net oil production being greater than 70%. 8. In a process as claimed in claim 7 wherein the coal is Illinois No. 6, the hydrogen throughput is 43 standard cubic feet per pound of coal, the conversion of moisture ash free coal is greater than 9. In a process as claimed in claim 7 wherein a solids free liquid is recovered from the reaction effluent and is used as the subsequently recovered liquid in step (b).

References Cited UNITED STATES PATENTS Re. 25,770 4/1965 Johanson 208-10 2,860,101 11/1958 Pelipetz 208-10 2,885,337 5/1959` Keith et al. 208-8 2,987,465 6/ 1961 Johanson 208-10 3,183,180 5/1965 Schuman et al. 208-143 3,321,393 5/1967 Schuman et al. 208-10 OTHER REFERENCES Petroleum -Products Handbook, Virgil B. Guthrie, 1st ed., McGraw-Hill, New York, 1960, chapter 8, pp. 25-26.

DANIEL E. WYMAN, Primary Examiner P. E. KONOPKA, Assistant Examiner U.S. Cl. X.R. 

